Knicks president Donnie Walsh said a misperception exists that his interest in the Rockets’ Tracy McGrady is solely as a rental to inject life into a dying season.

“There’s reasons other than that,” Walsh told The Post.

Walsh declined to specify, but a source said the Knicks would like to see if McGrady is someone to consider re-signing in July. At least they’d have a fallback candidate if McGrady excels and they are unable to land one of the top free agents, LeBron James or Dwyane Wade.

The other four top free-agent candidates are Joe Johnson, Chris Bosh, Carlos Boozer and Amar’e Stoudemire. McGrady once was considered in those players’ class before microfracture surgery on his left knee last year.

“I think he’s a very good player,” Walsh said. “The microfracture surgery is a concern for everybody. But he’s a good player. . . . I’ve been realistic about these first two years and I’m not doing this for immediate satisfaction.”

Walsh said the rumors of serious talks between the Rockets, Knicks and Wizards on a three-team trade have been inflated. Walsh said he first heard the three-team scenario through a media report. Since then, Walsh has contacted the Wizards and Rockets to find out if they were speaking about a potential three-way deal.

In addition, Walsh said he has other irons in the fire. The club is exploring Nate Robinson’s trade value. If the Knicks trade Robinson, they would open playing time for rookie Toney Douglas if they go to a youth movement.

Another source said the Rockets are talking to several teams, but nothing is close to being done on any front. The source said Al Harrington is the lone lock in a three-way deal and he would wind up in Washington.

McGrady is working out with trainer Tim Grover in Chicago.

“I definitely think he’ll be moved, I just don’t know where,” Grover said. He added that several teams have called him about McGrady, but he hasn’t spoken to the Knicks.